The present invention relates to a switch input processing module and, more particularly, to a switch input processing module in which either an analog signal system or a serial signal system is selectively connected to an external connection terminal, and which switches a signal transmitting state of a serial signal transmission line in accordance with the kind of a signal supplied which is either an analog signal or a serial signal.
Hitherto, as one of devices mounted on a vehicle, a signal transmitting device related to steering, which is disposed on or near a steering mechanism and transmits various signals is known. The signal transmitting device related to steering has: various manually-operated switches arranged near the steering wheel, a signal source which is disposed in the steering wheel and generates a signal corresponding to an operating state of each of the various manually-operated switches; a switch input processing module (base module) for dealing with an output signal from the signal source; and a cable reel connecting the signal source and the switch input processing module. In this case, the cable reel is disposed around a wheel shaft close to the coupling portion o the wheel shaft and the steering wheel. The cable reel takes the form of a flexible cable or the like which is spirally wound for coupling the signal source attached to the rotating steering wheel and the switch input processing module fixedly disposed in the wheel shaft holding portion.
The operation of the signal transmitting device related to steering will be briefly described as follows.
In the case where any one of the various manually-operated switches disposed near the steering wheel is operated, the signal source outputs a signal corresponding to the manually-operated switch, and the derived signal is supplied to a signal input port of the switch input processing module via the cable reel. In response to the supplied signal, the switch input processing module performs adjustment corresponding to the operating state of the manually-operated switch for a device such as an audio device mounted on the vehicle related to the operated manually-operated switch.
A known signal transmitting device related to steering selectively has an analog signal source for outputting an analog signal and a serial signal source for outputting a serial signal as signal sources. In accordance with a car model or the like of the vehicle, either the analog signal source or the serial signal source is selectively used. In this case, the analog signal source has various manually-operated switches and an analog multiplex (MPX) for outputting a voltage obtained by the operation of any of the manually-operated switches as an analog signal. The serial signal source has various manually-operated switches and a serial multiplex (MPX) for detecting an operating state of the manually-operated switches and outputting the detection output as a serial signal.
Depending on which one of the analog signal source or the serial signal source is used as a signal source, the configuration of the switch input processing module to be used differs. Specifically, in the case of using the analog signal source, an analog signal type switch input processing module capable of receiving and processing an analog signal has to be used. On the other hand, in the case of using the serial signal source, a serial signal type switch input processing module capable of receiving and processing a serial signal has to be used.
As described above, in the known signal transmitting device related to steering, whether the analog signal source or the serial signal source is used as a signal source is selectively set. Consequently, the switch input processing module has processing means which can deal with any signal source selected. In this case, according to first processing means, two kinds of switch input processing modules of an analog signal type switch input processing module and a serial signal type switch input processing module are prepared. In accordance with the kind of the signal source selected and used, the kind of the switch input processing module is selected. According to second processing means, a common switch input processing module having the function of both the analog signal type switch input processing module and the serial signal type switch input processing module is used as a switch input processing module. The common switch input processing module is provided with an external connection terminal capable of receiving an analog signal from an analog signal source and an external connection terminal capable of receiving a serial signal from a serial signal source. In accordance with the kind of the signal source selected and used, the external connection terminal of the common switch input processing module is selectively used.
The known signal transmitting device related to steering has processing means which can be adapted to any of the analog signal source or the serial signal source on the switch input processing module side. As the first processing, two kinds of modules of the analog signal type switch input processing module and the serial signal type switch input processing module have to be prepared. It makes the configuration of the whole switch input processing module complicated. Moreover, the manufacturing cost increases largely. On the other hand, as the second processing means, the common switch input processing module provided with the external connection terminal capable of receiving an analog signal and the external connection terminal capable of receiving a serial signal is used. Consequently, as compared with the first processing means, the configuration is less complicated and the manufacturing cost is slightly lower. However, it is not easy to achieve the common switch input processing module having the external connection terminals which can deal with the two kinds of signals and can receive the two kinds of signals separately. The configuration of the whole switch input processing module is still complicated and the manufacturing cost is still high.
The invention has been achieved in consideration of such a technical background. It is an object of the present invention to provide a switch input processing module having a simple configuration at low manufacturing cost, which uses an external connection terminal common to an analog signal and a serial signal and can selectively receive the analog and serial signals by a simple configuration change.
According to the invention, in order to achieve the object, there is provided a switch input processing module having: a control unit; a first external connection terminal to which either an analog signal from an analog signal system or a serial signal from a serial signal system is supplied; an analog signal transmission and serial signal transmission line which is disposed between the first external connection terminal and the control unit; and a second external connection terminal to which a determination signal indicating that either the analog signal system or the serial signal system is connected to the first external connection terminal is supplied, wherein when the control unit determines that the determination signal indicates connection of the serial signal system, the control unit makes the serial signal transmission line conductive, and when the control unit determines, that the determination signal indicates connection of the analog signal system, the control unit makes the serial signal transmission line nonconductive.
In such a configuration, the determination signal indicating whether the signal to be supplied is an analog signal or a serial signal is supplied to the control unit prior to the supply of the analog or serial signal. When the determination signal supplied is indicative of an analog signal, the control unit makes the serial signal transmission line nonconductive to thereby supply the analog signal only to the analog signal supply port. When the determination signal supplied is indicative of a serial signal, the control unit makes the serial signal transmission line conductive to thereby supply the serial signal only to the serial signal supply port via the serial signal transmission line. Thus, by making a simple configuration change, the switch input processing module can be commonly used by the analog and serial signal and, as a result, the switch input processing module with a simple configuration can be obtained at a low manufacturing cost.
According to the invention, the first and second external connection terminals may be connection terminals which are different from each other.
In such a configuration, the external connection terminal to which the determination signal is supplied can be provided separate from the external connection terminal to which the analog or serial signal is supplied. Consequently, the determination signal can be generated independent of the analog or serial signal.
Further, according to the invention, the first and second external connection terminals may be connection terminals which are the same.
In such a configuration, it is unnecessary to separately provide the external connection terminal to which the determination signal is supplied. The external connection terminal can be therefore effectively used.
According to the invention, preferably, the determination signal indicative of connection of the serial signal system is a voltage signal equal to a reference voltage, and the determination signal indicative of connection of the analog signal system is a voltage signal lower than the reference voltage.
In the configuration, when the control unit determines the determination signal, it is sufficient to see whether the signal is equal to or lower than the reference voltage. Thus, the determination signal can be easily determined.
According to the invention, preferably, the determination signal indicative of connection of the serial signal system is a pulse signal having a predetermined pulse width and/or a predetermined number of pulses.
In the configuration, the control unit can easily generate a determination signal prior to supply of the serial signal. When the control unit determines the determination signal, it is sufficient to measure the pulse width and/or the number of pulses by counting clock signals. The determination signal can be therefore easily determined.